It has long been known to impinge materials with suitable radiation, for example thermal radiation, and to detect the reflected amount of light from the respective material via a sensor. One example of this is the solution disclosed in European patent application 0 563 953 A2. A disadvantage of this solution is that the light detections depend heavily on the surface characteristics of the material. Such a solution is not suitable for the impingement of dental materials, because the existing degree of moisture of the dental materials would greatly affect the degree of reflection and lead to errors in measured values.
In order to provide a reliable detection of the energy impingement in every case, that is, the impingement by means of a light and/or heat source, U.S. Pat. No. 5,922,605 discloses the use of a sensor as a light sensor. The sensor is arranged outside of the actual radiation area and measures the brightness and/or heat in the outer field of the dental material, so that the disadvantages of the previously noted solution are avoidable.
On the other hand, the polymerization of the dental material used depends heavily on numerous factors. For example, polymerization of typical surface layers is faster than deeper layers of the dental material, which is used in dental restoration, for example.
For determining which polymerization time is favorable, it has been proposed already to determine the mass of the polymerization material and to adjust the polymerization time in dependence thereon. Also, numerous further features have been proposed in order to prevent a release of monomers with free radicals, caused by incomplete polymerization, as well as the formation of edge gaps of the dental restoration caused by an excessive polymerization time.
Not only different dental materials, but also, for example, parameters in individual cases affect the polymerization process, such as for example the storage time of the dental material before the application. In order to achieve an optimal polymerization result, one must realize practically an assay-polymerization with precisely the same form from the same charge of the polymerization material. This then will demonstrate and determine how the polymerization time should be adjusted. This method, naturally, is not practical.